An opinion Wednesday shows the Supreme Court is as divided as ever on whether congressional committee reports should be used to help understand what Congress meant when drafting and enacting a law.

All the justices agreed that the 2010 Dodd-Frank law only protects whistleblowers who tell the Securities and Exchange Commission about corporate wrongdoing. But the decision became a platform for justices to air their judicial philosophies about the long-contested idea of whether to give weight to legislative history.

The debate has become a staple in Senate judicial confirmation hearings, and an area for lawyers arguing before the justices to tread carefully. A 2010 study in the William and Mary Law Review found liberal justices are more likely to cite legislative history, and justices are more likely to consult legislative history when they are ideologically sympathetic to Congress’ purpose.

Wednesday’s opinion, written by Justice Ruth Bader Ginsburg, in part explores the “purpose and design” of the financial overhaul’s robust whistleblower program with citations to a Senate report. Such reports typically lay out for members of Congress and their staffs the purpose, policy implications and context of a bill.

For example, the opinion cites the report for the Dodd-Frank bill as stating that the “core objective” of the whistleblower program was “to motivate people who know of securities law violations to tell the SEC.”

Three of the conservative justices weren’t having it. Justice Clarence Thomas wrote a concurrence, and Justices Samuel A. Alito Jr. and Neil Gorsuch said they joined the opinion only as it relates to the text of the law itself.

“Even assuming a majority of Congress read the Senate Report, agreed with it, and voted for Dodd-Frank with the same intent, ‘we are a government of laws, not of men, and are governed by what Congress enacted rather than by what it intended,’” Thomas wrote.

“Legislative history is of course not the law, but that does not mean it cannot aid us in our understanding of a law,” Sotomayor wrote. “Just as courts are capable of assessing the reliability and utility of evidence generally, they are capable of assessing the reliability and utility of legislative-history materials.”

Her concurrence was joined by Justice Stephen G. Breyer, a Senate Judiciary Committee counsel in 1979-80 for Massachusetts Democrat Edward M. Kennedy.

“For these reasons, I do not think it wise for judges to close their eyes to reliable legislative history — and the realities of how Members of Congress create and enact laws — when it is available,” Sotomayor wrote.

That prompted Thomas to respond, in a footnote in his concurrence, that “for what it’s worth” he seriously doubts that a committee report is a “particularly reliable source.”

Thomas previously worked as a legislative assistant to Missouri Republican John C. Danforth on the Senate Commerce Committee.

To make his point, Thomas quotes at length an exchange on a tax bill from 1982 on the Senate floor between Republican Sens. Bob Dole of Kansas and William Armstrong of Colorado. It’s an exchange that also came up in Justice Antonin Scalia’s 1986 confirmation hearing when the Senate Judiciary Committee explored his views on the use of legislative history.

“Mr. President, has the senator from Kansas, the chairman of the Finance Committee, read the committee report in its entirety?” Armstrong asked.

“I am working on it,” Dole replied. “It is not a bestseller, but I am working on it.”

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Correction 5:16 p.m. | An earlier version of this story incorrectly stated that Justice Stephen G. Breyer was the only justice with experience working for the legislative branch on Capitol Hill.